In developing and starting up machine tools or robots, the development or installation engineer often encounters the problem, independently of the control task at hand, of having to properly adjust tightened controller configuration or pilot controls, and of being able to simply recognize their effects. For this, auxiliary measuring systems are usually needed, which, due to the level of accuracy required, entail substantial additional outlay for development and start-up operation. For example, to determine the operating accuracy of a machine tool, a plurality of expensive measuring instruments are used, often costing more than DM 150,000. In addition, such measuring instruments require specially trained personnel.
To perform a synchronous measurement, for example, one needs expensive acceleration sensors, a charge amplifier and spectral analyzers. Thus, for example, inductive displacement probes can be used, but only those having a ruler (i.e., straight-edge rule) of the highest possible surface quality, which entails correspondingly high costs. Besides the costs, when such auxiliary devices are used to determine synchronism, problems arise with respect to axial overlapping. In addition, spindle influences are not easily ascertained.
To determine positioning trueness (i.e. accuracy), inductive displacement probes are usually used. These are very slow, however. When working with optical encoders (i.e. indicators), the problem arises that the location where the position is measured--usually a glass scale--is not easily accessible.
To measure the contour trueness or other contour features, such as corners, using conventional methods, a very time-consuming workpiece measurement is required. For this, in turn, expensive measuring instruments are needed.
To perform a test of circularity, conventional methods require a circular calibration standard having a two-dimensional probe head, which entails costly adjustment with respect to the circle center. In addition to this, a separate circular calibration standard is required for each circle radius. The costs this entails are substantial and, depending on the (i.e. required) accuracy, amount to over DM 100,000.
Similarly, by enlarging a segment (i.e. detail) of the setpoint path and the actual path, the trueness of contour can be determined, it no longer being possible in this case to examine the entire path curve, since enlargement factors within the range of 100 to 1000 are needed.
European Patent Application No. 165 436 describes a method for programming robot movements in a manner the economizes on memory space. To determine and optimize the synchronism, the causes of inaccuracies are determined by performing a spectral analysis on the path deviation values, in particular by performing a Fourier analysis. In this manner, besides a programming that economizes on memory space, the dynamic performance of the robot being used is able to be described by a transfer function, rendering possible a speed-independent compensation of the robot's dynamic performance in the spectral region.
A method for testing the operating accuracy of an NC machine is described in International Patent Application No. 94/07187. The operating accuracy of the NC machine is checked by comparing a circular setpoint path to an actual circular path that describes the machine's actual motion in accordance with a position control signal that describes the setpoint path of motion. However, this is only possible for an at least two-axis NC machine. Also, the method is limited to a circular setpoint path.
A method for determining the operating accuracy of a numerically controlled machine is described in European Patent Application No. 510 204. Positions which occur in response to the corresponding actuating signals for the machine axes in question are periodically detected in the X and Y direction. The setpoint path is contrasted to the active actual path, and it is checked whether deviations lie within the scope of a permitted range or exceed the range.